1. Field of the Invention
This invention relates to a catheter device having a shaft, a rapid-exchange guidewire lumen (one which terminates at a proximal guidewire exit port that is distal of the proximal end of the catheter) and a distal end which exhibits a sheath which can be withdrawn proximally to release a self-expanding implant such as a stent. To prevent the self-expanding stent moving proximally with the proximally-moving sheath, the catheter device includes a stopper which bears on the stent and resists its proximal movement.
2. Background Prior Art
Conventionally, such a catheter device exhibits a shaft comprising an outer tube connected to the sheath and an inner shaft connected to the stopper, whereby the proximal movement of the sheath is accomplished by imposing an endwise tension on the outer tube, with the inner shaft carrying an endwise compression stress, as the stopper at the distal end of the inner shaft works to resist proximal movement of the stent. For examples, see WO 03/003944, WO 03/002020, WO2004/062458 and EP-A-1095634.
US 2004/0220653 A1 provides delivery and deployment apparatuses for bifurcated stents capable of comfortably cradling the corina of bifurcated target tissue between the arms of the bifurcated stents as each arm of the bifurcated stent is delivered to a respective side branch.
Such conventional systems can work well, and can be of relatively simple construction. However, the present inventor has discovered that they are nevertheless capable of improvement.
One disadvantage noted by the present inventor is that release of the stent requires the medical practitioner to maintain the inner pusher shaft unchanged in axial disposition relative to the site of stenting in the body of the patient, while pulling back on the outer tube of the shaft to release the stent. This pulling back of the outer tube requires relative movement of the outer tube in the bodily lumen (or guide catheter) in which it has been advanced to the site of stenting. Any friction or resistance to axial movement of the outer tube in the lumen in which it is located hinders the objective of maintaining the stopper in a precise disposition relative to the target stenting site. In practice, it is customary to compensate for axial strain in known systems by positioning the stent slightly distal of the desired end position before commencing stent deployment by pulling back the sleeve. The present invention aims to reduce or eliminate the need for such compensation.